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Author Topic: i need some help with a ft-101e blowing the main fuse, over my head  (Read 1303 times)
KC7BYP
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« on: April 07, 2013, 11:15:44 PM »

I picked up a Yeasu ft-101e knowing that it was working then stopped working and is blowing the ac fuse. I fig it would be an easy fix.  1st off the radio tries to start up when I hit the power switch then blows the fuse.  When I pull the voltage regulator board the ac supply stop's blowing the fuse.  I did a manual ohms check on the voltage regulator and found nothing wrong.  I also found out with the jones plug unpluged and I apply 12vdc to pin 1 of the jones plug I can get the receiver 100% working.  I tried wiring up an exture jones plug for 12vdc.  The receiver was working with a strange ticking sound in the speaker.  I had to unplug the radio after like a minute.  The main red and black leads to the battery were over heating. If I apply the 12vdc directly to pin 1 on the jones plug I can run the receiver for hours with no problems and no ticking sound. After I started poking around in the bottom side of the power supply I found a solder bridge, on the primary side of the transformer, between one of the 117vac tap and the low side of the primary winding.  Removing that solder bridge removed the short across the ac power cord.  But it is still poping the fuse (it takes a bit longer to pop the fuse now).  Many of the transformer tabs look like they have been worked on (to much solder and to much heat).  The wiring diagram shows the fuse tip is suppose to go to ground. the fuse tip is going to one of the 117vac primary taps and an other line going to I think is the 160vac on the other primary tap. Please correct me if I am wrong, with a dual, multi voltage, primary taped power transformer.  Both primary's need to be set to the same voltage or the power supply will go poof.  I need to know if the one primary winding tap should be on 117vac and the other primary should be on 160vac.


Steve-kc7byp   
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K1CJS
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« Reply #1 on: April 09, 2013, 04:55:38 AM »

This is just one of the causes that may be affecting your rig, but it's the most likely. 

Somewhere in the power supply chain there may be a shorted capacitor.  You'll have to lift one side of each capacitor connection and meter it to find it.  Start with the electrolytics.  Once you replace the bad capacitor/capacitors, you should be able to stop the fuses from blowing.

Note that if there are capacitors that are bad, there may well be other components that are either bad or that have changed value with age.  To get the rig back to a dependable operating condition, you may have a rather big job on your hands.  Good luck!
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KC7BYP
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« Reply #2 on: April 09, 2013, 08:21:10 PM »

I finely solved the problem.  The person that had the radio before me didn't know how to properly tune the final tubes. All 3 tubes are shorted out and show signs of been exposed to extremely high heat from driving the tubes to hard.  Also transistors Q1 and Q2 in the power supply are shorted out and R5 in the power supply is glowing red from to much current been run through it because Q1 and Q2 are shorted out.

Steve
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K1CJS
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« Reply #3 on: April 10, 2013, 11:01:15 AM »

It's always nice to find that out--after the fact, isn't it?  I didn't take that into account, not at all.

On the other hand, it's possible that the previous owner was an 'appliance operator' and didn't have the knowledge to realize that his antenna system wasn't properly built, or simply not properly matched to the 101.

In any event, glad you've got it figured out.  73!
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W8AAZ
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« Reply #4 on: April 10, 2013, 03:23:01 PM »

Also there is a SM cap in the bandswitching that shorts occasionally and causes a power short but it only reveals itself when you select 160M.
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